Discharge means in a centrifugal drier

ABSTRACT

The discharge means for a centrifugal drier comprises a vibratory hopper fluid-tightly connected at one end thereof to the outlet of the drier casing which received the dried particles and is filled with a gaseous fluid under a pressure exceeding that of the ambient atmosphere. A vertical discharge conduit is fluid-tightly connected to the opposite end of the vibratory hopper and holds a column of the removed dried particles. The length of the conduit is such that the loss of pressure of the gaseous fluid passing from the casing through the column of dried particles is substantially equal to the pressure differential between the gaseous fluid in the casing and the ambient atmosphere. A control valve at the lower end of the discharge conduit is so regulated that the output of the particles from the conduit maintains the level of the dried particles in the hopper above a set minimum level.

United States Patent [191 Mercier Nov. 11, 1975 [75] Inventor: AndrMercier, La Madelaine,

France [73] Assignee: Fives-Cail Babcock, Paris, France [22] Filed:Sept. 27, 1974 [21] Appl. No.: 509,914

[30] Foreign Application Priority Data Sept. 27, 1973 France 73.34614[52] US. Cl. 34/58; 34/56; 34/164 [51] Int. Cl. F2613 17/24 [58] Fieldof Search 34/43, 52, 55, 56, 58, 34/164, 176, 170; 198/57; 210/360 R[56] References Cited UNITED STATES PATENTS 2,834,658 5/1958 Lieffers eta1 34/56 2,880,519 4/1959 Pollock 34/58 3,553,846 1/1971 McKenzie et al34/56 3,618,227 11/1971 Breakell et al 34/164 FOREIGN PATENTS ORAPPLICATIONS 618,502 8/1935 Germany 34/34 Primary Examiner-Kenneth W.Sprague Assistant Examiner.lames C. Yeung Attorney, Agent, or FirmKurtKelman [57] ABSTRACT The discharge means for a centrifugal driercomprises a vibratory hopper fluid-tightly connected at one end thereofto the outlet of the drier casing which received the dried particles andis filled with a gaseous fluid under a pressure exceeding that of theambient atmosphere. A vertical discharge conduit is fluid-tightlyconnected to the opposite end of the vibratory hopper and holds a columnof the removed dried particles. The length of the conduit is such thatthe loss of pressure of the gaseous fluid passing from the casingthrough the column of dried particles is substantially equal to thepressure differential between the gaseous fluid in the casing and theambient atmosphere. A control valve at the lower end of the dischargeconduit is so regulated that the output of the particles from theconduit maintains the level of the dried particles in the hopper above aset minimum level.

4 Claims, 1 Drawing Figure US. Patent Nov. 11, 1975 3,918,170

DISCHARGE MEANS IN A CENTRIFUGAL DRIER The present invention relates toimprovements in the continuous drying of liquid-solid mixture, such assugar juice, and more particularly to a type of centrifugal drier forthe continuous production of dried solid particles, which comprises arotary drying basket, a fluidtight casing defining a chamber arranged toreceive the solid particles centrifugally ejected from the basket andfilled with a gaseous fluid under a pressure exceeding that of theambient air outside the casing to increase the drag on the particlesalong their trajectory in the chamber, the casing having an outlet forremoving the dried particles therefrom, and a discharge meansfluidtightly connected to the outlet. I have disclosed and claimed acentrifugal drier of this type in my US. Pat. No. 3,821,857, dated July2, 1974, whose entire disclosure is herewith incorporated by reference.

In my patent, the disclosed discharge means is a gastight rotary gate.This, however, has been found notalways to give satisfactory results,particularly when the dired material is sticky, such as sugar. It alsois unsatisfactory when the pressure differential between the inte riorof the casing and the ambient atmosphere is too great. If a lock chamberis used, the-particle discharge is discontinuous and dried particles areaccumulated from time to time at the outlet of the casing. This wouldmake the device inoperative for the treatment of sugar, for instance,since the accumulated sugar particles would block the outlet. Therefore,a double lock chamber would have to be used and controlled automaticallyfor cycles of alternative openings to assure a continuous discharge.Such an automatic system is complicated and expensive.

It is the primary object of this invention to provide a simple dischargemeans for a centrifugal drier of the indicated type, which assure aregular continuous output, functions with considerable pressuredifferentials between the interior of the casing and the ambientatmosphere, and comprises no mobile parts whose movements may be impededby deposits of solid particles.

The above and other objects are accomplished in accordance with theinvention with a discharge means including a vibratory hopperfluid-tightly connected at one-end thereof to the outlet of the casingand a vertical discharge conduit fluid-tightly connected to the oppositeend of the vibratory hopper. The discharge conduit holds a column of theremoved dried particles and the length of the discharge conduit is suchthat any escape of the gaseous fluid passing from the casing through thecolumn of removed dried particles is minor, i.e. has a small value. Acontrol valve at the lower end of the discharge conduit controls theoutput of dried particles from the discharge conduit and means 1Referring now to the drawing, the conical outlet bottom 10 is part of acentrifugal drier casing such as fully shown and described in myabove-mentioned U.S. patent. This casing is filled with a gaseous fluidunder pressure and the dried particles received therein must becontinuously removed through the outlet without permitting thecompressed air in the casing to escape to the atmosphere. The dischargemeans of this invention is designed to accomplish this purpose. Itincludes vibratory hopper 12 fluid-tightly connected at one end thereofto outlet 10 of the casing my means of flexible sleeve 14. The flexiblesleeve may be of natural or synthetic rubber, for instance, and its endsare affixed to connecting flanges on the casing and hopper,respectively. Vertical discharge conduit 16 is fluid-tightly connectedto the opposite end of vibratory hooper 12.

The vibratory hopper comprises a cylindrical upper portion and afrusto-conical lower portion, and valve 18 for stopping the flow ofparticles is arranged between the lower portion of the hopper and theupper end of vertical discharge conduit 16. In the illustratedembodiment, valve 18 comprises a deformable cylindn'cal sleeveinterconnectingrespective flanges at the opposite end of hopper l2 andthe upper end of discharge conduit 16, and a housing surrounding thedeformable sleeve. A fluid may be introduced into the space between thehousing and the deformable sleeve to constrict the latter so as torestrict or close communication between the hopper and the discharge.conduit whereby the flow of particles may be restricted or stopped.

A suitable vibrator 20 of any known design is attached to hopper 12 forsubjecting the same to suitable vibrations of a low amplitude; Flexibleconnecting sleeve 14 prevents these vibrations from being transmitt'edto the casing of the centrifugal drier. If desired, a similar flexibleconnecting sleeve may be arranged between the hopper and the dischargeconduit to accomplish alike purpose, thus isolating the vibrations ofthe hopper from all other parts of the drier.

Control valve 22 is mounted at the lower end of discharge conduit 16 forcontrolling the output of dried particles from the discharge conduit,this output determining the level of the dried particles in the hopperwhich receives the particles from the casing by gravity feed, and theparticles being gravity fed from the hopper into the discharge conduitaccording to the setting of valve 18.

Automatic control 24 constitute means for regulating control valve 22 sothat the output of the particles from the conduit maintains the level ofthe dried particles in the hopper above set minimum M. In the disclosedembodiment the control is so set that it maintains the level of thedried particles in the hopper at a level between set maximum level M andminimum level M. For this purpose, sensors are mounted in the hopper atthe set minimum and maximum levels to. sense the column of particles inthe hopper. On sensing particles at that level, the sensors producerespective control signals electrically transmitted to control 24 and anelectric control circuit 25 connects the control to valve 22 forregulating the same in response to the control signals.

An alarm system 26, incorporating a sensor at a set maximum level Mwarns tthe operator by a visible and/or audible signal if the particlesin the hopper reach this upper limit. Alternatively, this alarm systemmay be connected directly to a control system which regulates the feedto the drier so as to control this feed in response to this upper levellimit in the discharge hopper.

An arcuate deflecting guide or baffle 28 is pivotally mounted at thelower output end of discharge conduit 16 to permit the dischargedparticles to be directed to a desired location, such as endless conveyorband 29 mounted below the discharge conduit to convey the dischargedsolid particles away from the drier.

The particles are conveyed through the discharge means by the pressureof the gaseous fluid in the casing.

In accordance with the present invention, the length of dischargeconduit 16 is so selected that any escape of the gaseous fluid passingfrom the casing through the column of removed dried particles in thedischarge conduit is minor. Any such loss of gaseous fluid is producedby the flow of the gaseous fluid through the col umn of particles indischarge conduit 16 and in hopper 12 when the level of the particles inthe hopper is between minimum level M and maximum level M Under thiscondition, the escape of air from the casing into the atmosphere throughthe discharge means is to]- erable.

Control 24 maintains the level of the particles in the hopper betweenlevels M and M by regulating the opening of valve 22. Since the surfaceof the column of particles in the hopper is not plane, a mean levelbetween M and M is maintained. The level sensors for the control maycomprise a radioactive source emitting gamma radiation and a detectormeasuring the intensity of the emitted radiation across the hopper.

To make the control responsive in sufficient time to effectuate thevalve regulation, the level control must be effected in a zone where theparticles move relatively slowly. For this reason, the control iseffectuated in hopper 12 rather than in discharge conduit 16 because theparticles move much more slowly down the frusto-conical hopper than theconduit.

When the output of solid particles is small, for instance towards theend of the drying procedure, and control 24 must close valve 22 tomaintain the level of particles above set minimum level M, the controlcircuit is de-energized to permit automatic evacuation of the hopper andthe discharge conduit. The discharge means then functions like a lockchamber, with valve 18 closed and valve 22 open, or vice versa. Thisprevents clogging of the discharge means.

Throughout the specification and claims, the term minor escape of thegaseous fluid passing from the casing through the column of removeddried particles is meant to designate an amount of gaseous fluid escapeof such magnitude that the power necessary for compensating for suchescape and to maintain the pressure in the casing at the set value isnegligible in relation to the total power consumed by the drier.

I claim:

1. In a centrifugal drier for the continuous production of dried solidparticles, which comprises a fluidtight, closed casing arranged toreceive the dried parti cles and filled with a gaseous fluid under apressure exceeding that of the ambient air outside the casing, thecasing having an outlet for removing the dried particles therefrom: adischarge means fluid-tightly connected to the outlet, the dischargemeans including 1. a vibratory hopper fluid-tightly connected at one endthereof to the outlet of the casing,

2. a vertical discharge conduit fluid-tightly connected to the oppositeend of the vibratory hopper,

a. the discharge conduit holding a column of the removed dried particlesand b. the length of the discharge conduit being such that any escape ofthe gaseous fluid passing from the casing through the column of removeddried particles is minor,

3. a valve between the opposite end of the hopper and the dischargeconduit for controlling the flow of particles from the hopper into thedischarge conduit,

4. a control valve at the lower end of the discharge conduit forcontrolling the output of dried particles from the discharge conduit,and

5. means for regulating the control valve so that the output of theparticles from the conduit maintains the level of the dried particles inthe hopper above a set miniumum level.

2. In the centrifugal drier of claim 1, a flexible sleeve fluid-tightlyconnecting the outlet of the casing to the one end of the hopper.

3. In the centrifugal drier of claim 1, the regulating means comprisingan automatic control maintaining the level of the dried particles in thehopper at a level between set maximum and minimum levels.

4. In the centrifugal drier of claim 1, an alarm system responsive to aset maximum level of the dried particles in the hopper.

1. In a centrifugal drier for the continuous production of dried solidparticles, which comprises a fluid-tight, closed casing arranged toreceive the dried particles and filled with a gaseous fluid under apressure exceeding that of the ambient air outside the casing, thecasing having an outlet for removing the dried particles therefrom: adischarge means fluid-tightly connected to the outlet, the dischargemeans including
 1. a vibratory hopper fluid-tightly connected at one endthereof to the outlet of the casing,
 2. a vertical discharge conduitfluid-tightly connected to the opposite end of the vibratory hopper, a.the discharge conduit holding a column of the removed dried particlesand b. the length of the discharge conduit being such that any escape ofthe gaseous fluid passing from the casing through the column of removeddried particles is minor,
 3. a valve between the opposite end of thehopper and the discharge conduit for controlling the flow of particlesfrom the hopper into the discharge conduit,
 4. a control valve at thelower end of the discharge conduit for controlling the output of driedparticles from the discharge conduit, and
 5. means for regulating thecontrol valve so that the output of the particles from the conduitmaintains the level of the dried particles in the hopper above a setminiumum level.
 2. a vertical discharge conduit fluid-tightly connectedto the opposite end of the vibratory hopper, a. the discharge conduitholding a column of the removed dried particles and b. the length of thedischarge conduit being such that any escape of the gaseous fluidpassing from the casing through the column of removed dried particles isminor,
 2. In the centrifugal drier of claim 1, a flexible sleevefluid-tightly connecting the outlet of the casing to the one end of thehopper.
 3. In the centrifugal drier of claim 1, the regulating meanscomprising an automatic control maintaining the level of the driedparticles in the hopper at a level between set maximum and minimumlevels.
 3. a valve between the opposite end of the hopper and thedischarge conduit for controlling the flow of particles from the hopperinto the discharge conduit,
 4. a control valve at the lower end of thedischarge conduit for controlling the output of dried particles from thedischarge conduit, and
 4. In the centrifugal drier of claim 1, an alarmsystem responsive to a set maximum level of the dried particles in thehopper.
 5. means for regulating the control valve so that the output ofthe particles from the conduit maintains the level of the driedparticles in the hopper above a set miniumum level.